1. Field of the Invention
The present invention relates to a spoke type permanent magnet motor, and more particularly, to a permanent magnet motor of an outer rotor type formed in a multipolar spoke type.
2. Description of the Related Art
As enclosed in Korean Examined Patent Publication 10-548716, a spoke type motor, as shown in FIG. 1, includes a rotor 1 having a number of permanent magnets 3, and a stator 2 having a number of slots 2a wound with coils and enclosing the outside of the rotor 1.
The permanent magnet 3 of the rotor 1 is radially disposed on a rotation shaft (not shown). The rotor 1 supports the permanent magnet 3 and includes a cylindrical core 4 forming paths of magnetic flux. The core 4 is formed with a number of steel plates laminated in an axis direction and includes a number of magnet coupling holes 4a for coupling a number of permanent magnets 3. Further, the core 4 includes a supporting section 4b for supporting the magnets 3 at an inner circumference section near the rotation shaft. The core 4 is integrally connected by the supporting section 4b.
However, the rotor of the motor shown in FIG. 1 causes magnetic flux leakage through the supporting section 4b because the inner circumference section of the core near the rotation shaft is connected by the supporting section 4b. That is, there is the magnetic flux leakage because magnetic flux is flowed through magnetic material, that is, the supporting section 4b. The size of the magnet 3 or the amount of the magnet is increased in consideration of such a magnetic flux leakage in a prior art, but, in this case, the bulk of the rotor 1 is increased and manufacturing cost is increased. Particularly, in order to achieve high efficiency, expensive neodymium magnet is used, wherein the neodymium magnet is expensive, thereby to increase manufacturing cost.
Further, the spoke type motor has an advantage capable of increasing the output density by small amount of the permanent magnet, but the demagnetization phenomenon of the permanent magnet is easily generated as compared with different type of the permanent magnet motor.